Patent GB-920897-A (GB)
Title: Improvements in or relating to sewing machines
IPC: D05B/
Filed: 1961-11-22
Abstract: 920,897. Sewing machines. MEFINA S.A. Nov. 22, 1961 [Nov. 26, 1960], No. 41830/61. Class 112. [Also in Group XIX] A sewing-machine adapted to produce a predetermined pattern of stitches comprises an element associated either with the needle or with the work-feed means and arranged to be positively advanced and resiliently returned once during each revolution of the main drive shaft of the machine, a programme member arranged to be advanced by one step for each revolution of the main shaft and having information tracks each of which corresponds to a definite position of the element, a member adapted to scan all the information tracks during each revolution of the main shaft, electronic means arranged to receive a pulse each time the scanning member receives information from a track, and means controlled electrically by the electronic means in such a way as to stop the element during the resilient return thereof in a position corresponding to the track conveying information to the scanning member. As shown, a zig-zag sewing-machine has a needle bar 3 mounted in a gate 4 pivoted about a vertical axis 5. A pin 7 pivoted to an arm 4a of gate 4 is biased by a spring 6 against a face cam 8 which is fixed to the main shaft 1 and is formed with a crest 8c flanked by leading and trailing rises 8a and 8b respectively. A toothed sector 4b on gate 4 is adapted to be engaged by a pin 9 to halt the gate. A lamp 16 is mounted in a cylinder 17 having an axial slot 18. A scanning member 19, carried by a hub 19a journalled on a shaft 20 coaxial with cylinder 17, is coupled by a chain 24 and sprockets 23, 25 of equal size to shaft 1. A rotatable cylinder 13 carries sprockets 14 engageable with spaced apertures 15 at the respective edges of an opaque film 11 which underlies the slot 18. A toothed pinion 27, rigid with cylinder 13, is engageable by a pin 26 rigid with hub 19a, to advance the film 11 by a step equal to the spacing of the apertures 14 for each revolution of the shaft 1. The film 11 is provided with ten parallel lines or tracks of translucent windows 12 so arranged that one window is aligned with each successive pair of opposed apertures 15. The scanning member 19, which is of part-cylindrical form concentric with cylinder 13 and extending over the film 11, has a helical leading edge 22 and a trailing edge 21 formed with ten steps each aligned with a line of apertures 12. The arrangement is such that while the pin 7 is being drawn by the spring 6 along the trailing edge 8b to retract the gate 4, one of the steps in edge 21 becomes aligned with a window 12 and the slot 18. Light from lamp 16 thereby falls on a photoelectric cell 36 so connected to a thyratron 28 and double diode 31, that the thyratron discharges to energize a solenoid 10, whereby pin 9 is moved into engagement with toothed sector 4b against the bias of a spring 37. Gate 4 is thus halted at a stitch-forming position corresponding to the position of the light-passing window 12. In an alternative arrangement pin 7 is shown attached to a work-feeding member. It is stated that the rotary member 19 may be replaced by a reciprocating scanning member.